Carbon-fiber reinforced plastics (hereinafter referred to as CFRP) have good advantages over other fiber reinforced plastics in mechanical characteristics, such as strength, modulus of elasticity, and lightness. For this reason, CFRP has found use in various applications in such fields as aircraft, spacecraft, sports, and equipment for leisure time amusement, and indeed the demand therefor is on the increase. Conventionally, however, CFRP has a drawback that it is not well qualified in respect of impact resistance and toughness, though it has high strength and high modulus of elasticity. As such, improvement in this respect is required in order that CFRP may be found satisfactory for use as a structural material for aircrafts and the like.
In order to overcome such a drawback of CFRP in respect of impact resistance and toughness, there have been developed hybrid plastics comprising carbon and aramid fibers. Also, as described in Japanese Patent Laid-Open Publication No. SHO 58-90943, there has been proposed a fiber reinforced composite material comprising carbon fiber and aromatic polyamide fiber.
However, with the known hybrid plastics, one problem is that in order to obtain improved toughness and impact resistance, the hybrid plastic must contain a considerably large amount of aramid fiber, which may adversely affect the elastic property feature which is characteristic of carbon fiber. Another problem is that the aramid fiber component exhibits poor performance in respect of wettability and adhesivity relative to the matrix resin, which fact may easily affect the rigidity and strength characteristics of the hybrid plastic, thus lowering the quality reliability of the plastic.
In the above cited Japanese Patent Laid-Open Publication No. SHO 58-90943, it is stated that the fiber reinforced composite material comprising carbon and aromatic polyamide fibers utilizes respective advantages of the two kinds of fibers, whereby respective shortcomings of the two fibers, i.e., insufficient impact resistance of the carbon fiber and low elasticity modulus of the aramid fiber, can be satisfactorily overcome, and more particularly improvement can be obtained in impact resistance and in adhesion property relative to the matrix resin, over "KEVLAR" (Registered trademark of Du Pont), a typical aramid fiber. However, this fiber reinforced composite material still has a problem in that its mechanical characteristics, such as strength, elasticity modulus, and impact resistance, are insufficient for use in the above mentioned applications, and improvement in this respect has been demanded.
It is a primary object of the invention to provide a carbon fiber prepreg and a carbon fiber reinforced material made from the prepreg which provide improved impact resistance and toughness and improved wettability and adhesivity relative to the matrix resin, without detriment to the outstanding characteristics of the carbon fiber component, and which can thus exhibit improved quality reliability and meet the foregoing demand in respect of all the performance characteristics required of fiber reinforced materials in general.